High-voltage power generation systems are used for, for example,
supplying regulated high-voltage direct current (DC) to a vacuum tube, which pushes
electrons to flow from a cathode to an anode and generates X-ray emission. The
power generation system typically includes a transformer module which has a high
secondary-to-primary turns ratio and converts a relatively low-voltage alternating
current (AC) to a relatively high-voltage AC. The power generation system may
further include a voltage multiplier module which utilizes diodes and capacitors to
further boost the high-voltage AC from a secondary winding of the transformer
module, as well as to convert the high-voltage AC into the targeted high-voltage DC.
In a conventional power generation system, the transformer module
includes at least two transformers and the multiplier module includes at least two
multipliers electrically connected in series and each coupled to a corresponding
transformer. When the number of the multipliers is too small, in order to achieve a
high-voltage DC output, each multiplier must include many diodes of one type
coupled in series and capacitors coupled in series, and the capacitors must have large
capacitances. The diodes in series exhibit a voltage unbalance effect due to a reverse
recovery process of the inconsistent series diodes, and induce over voltage damage.
When the number of the multipliers is too large, the multipliers and the transformers
need a lot of room, which in tum results in a bulky package and an increased cost.
BRIEF DESCRIPTION
In accordance with one embodiment disclosed herein, a power
generation system includes an input to receive a low-voltage alternating current and a
number N of voltage-conversion modules coupled to the input and each electrically
connected in series. Each voltage-conversion module includes a transformer for
converting the low-voltage alternating current into a high-voltage alternating current.
2
Each voltage-conversion module includes a multiplier for converting the high-voltage
alternating current from the transformer into a high-voltage direct current. The
multiplier includes a positive multiplier part and a negative multiplier part. The
positive multiplier part and the negative multiplier part each includes a pair of input
terminals connected in parallel with the transform and at least one multiplier stage
comprising a single diode and a capacitor assembly. The number N is an even
number between 4 and 24.
DRAWINGS
These and other features and aspects of the present disclosure will
become better understood when the following detailed description is read with
reference to the accompanying drawings in which like characters represent like parts
throughout the drawings, wherein:
FIG. 1 is a schematic diagram of a power generation system in
accordance with an exemplary embodiment;
FIG. 2 is a circuit diagram of an X-ray generation system using the
power generation system of FIG. 1;
FIG. 3 is a perspective VIew of a power generation package in
accordance with an exemplary embodiment; and
FIG. 4 is a cross-sectional view of the power generation package taken
along line 3-3 in FIG. 3.
DETAILED DESCRIPTION
Unless defined otherwise, technical and scientific terms used herein have
the same meaning as is commonly understood by one of ordinary skill in the art to
which this disclosure belongs. The terms "first", "second", and the like, as used
herein do not denote any order, quantity, or importance, but rather are used to
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distinguish one element from another. Also, the terms "a" and "an" do not denote a
limitation of quantity, but rather denote the presence of at least one of the referenced
items. The use of "including," "comprising" or "having" and variations thereof herein
are meant to encompass the items listed thereafter and equivalents thereof as well as
additional items. The terms "connected" and "coupled" are not restricted to physical
or mechanical connections or couplings, and can include electrical connections or
couplings, whether direct or indirect.
Referring to FIG. 1, a power generation system 100 according to one
embodiment of the invention includes a number N of voltage-conversion modules 1
each electrically connected in series for converting a low-voltage alternating current
(AC) into a high-voltage direct current (DC). According to an exemplary
embodiment, the number N is an even number between 4 and 24, including 4 and 24.
However, any suitable number of voltage-conversion modules I can be used as
necessary. Each voltage-conversion module 1 includes a transformer 11 for
converting the low-voltage AC into a high-voltage AC and a multiplier 12 electrically
coupled to the transformer 11 for further boosting the high-voltage AC from the
transformer 11 to an even higher-voltage AC as well as converting the higher-voltage
AC into a high-voltage DC.
Referring to FIG. 2, an exemplary embodiment is shown where the
power generation system 100 is used in an X-ray generation system 200 for providing
a targeted high-voltage DC to an X-ray tube 2. The targeted high-voltage DC is a
sum of the high-voltage DCs from the voltage-conversion modules 1. The X-ray tube
2 has a vacuum tube 21, an anode 22 and a cathode 23 electrically coupled to the
power generation system 100. The targeted high-voltage DC from the power
generation system 100 pushes electrons to flow from the cathode 23 to the anode 22
to induce X-ray emission. In certain embodiments, the targeted high-voltage DC
applied on the anode 22 and the cathode 23 ranges from 40 kV to 160 kV, for
example, for medical application, and an X-ray intensity is between 20 rnA to 1 A, for
example. However, the targeted high-voltage DC can be set to any value as required
by the application. The same is true for the X-ray intensity.
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The X-ray generation system 200 includes a power source 3 for
providing the low-voltage AC to the transformers II of the power generation system
100. The power generation system 100 includes an input 101 to receive the lowvoltage
alternating current from the power source 3. The power source 3 is an AC
power source that can output a lower voltage AC signal. In another embodiment, the
power source 3 may include a DC power source and an inverter converting a lowvoltage
DC from the DC power source to a low-voltage AC. In certain embodiments,
the power source 3 may further comprise a filtering circuit (not shown). In one
embodiment, a voltage amplitude of the low-voltage AC of the power source 3 may
be about a few hundreds of volts, and a switching frequency of the low-voltage AC
from the power source 3 ranges from 100 kHz to 1 MHz, for example. The voltage
amplitude and switching frequency can be set as necessary for the application.
With continued reference to FIG. 2, in certain embodiments, the
transformer 11 includes a core Ill, a primary winding 113 and a secondary winding
115. The low-voltage AC from the power source 3 is inputted through the primary
winding 113. The core III is a ferrite core, a nanocrystalline core or one of other
cores. The nanocrystalline core can be used when the switching frequency of the lowvoltage
AC is around 100 kHz. When the switching frequency of the low-voltage AC
is high, such as above 300 kHz, the ferrite core is more preferred. In the illustrated
embodiment, the primary windings 113 of the transformers 11 are electrically
connected in series. In certain embodiments, the primary windings 113 of the
transformers 11 are electrically connected in parallel to the power source 3. The
secondary winding 115 includes a pair of output terminals 116, 117 through which the
high-voltage AC is output. The high-voltage AC output from the transformer 11
ranges from 300 V to 5000 V, for example. However, the high-voltage AC can be set
to any value as required by the application.
Referring to FIGS. 1 and 2, each multiplier 12 is a bipolar multiplier and
includes a positive multiplier part 13 and a negative multiplier part 14. The positive
multiplier part 13 and the negative multiplier part 14 each includes a pair of input
terminals 131, 132, 141 and 142 connected with the output terminals 116, 117 of the
5
secondary winding 115 in parallel. The positive multiplier part 13 and the negative
multiplier part 14 are each a unidirectional multiplier circuit and respectively rectify
and amplify the high-voltage AC output of the transformer 11 into a high-voltage
positive DC at a positive DC output 133 and a high-voltage negative DC at a negative
DC output 143. Output terminals 133, 143 of adjacent multipliers 12 are connected in
series, and thus, a total output of the power generation system 100 can be represented
as a sum of the output voltages of the multipliers 12 of the voltage-conversion
modules 1. The high-voltage DC output from the multiplier 12 ranges from 1.5 kV to
40 kV, for example. However, the high-voltage DC output from the multiplier 12 can
be set to any value as required by the application. In certain embodiments, the
multipliers 12 have the same voltage input from the transformers 11 and the same DC
output.
The positive multiplier part 13 and the negative multiplier part 14 each
include at least one multiplier stage 15 comprising a single diode 151 and a capacitor
assembly 152. The diode 151 is not easily damaged by an unequal voltage. The
diode 151 can be a surface mounted diode with a voltage rating ranging from 600 V to
10 kV, such as 600 V, 1200 V, 3300 V, 6500 V, 10 kV and so on. The capacitor
assembly 152 comprises one or more serially connected capacitors and each capacitor
is a surface mounted capacitor with a voltage rating ranging from 600 V to 10 kV,
such as 600 V, 1200 V, 3300 V, 6500 V, 10 kV and so on. However, the diodes 151
and the capacitors can be other types and set to any value as required by the
application. In certain embodiments, the number of the multiplier stages 15 in each of
the positive multiplier part 13 and the negative multiplier part 14 is between 2 and 8,
including 2 and 8. However, the number of the multiplier stages 15 can be set to any
value as required by the application.
FIGS. 3 and 4 illustrate an exemplary power generation package 300 of
the power generation system 100 as described with respect to FIGS. 1 and 2.
Referring to FIGS. 3 and 4, the illustrated power generation package 300 includes a
printed circuit board 4 carrying electronic elements 151, 152 and a transformer
module 5 assembled by the number N of the transformers 11. The electronic elements
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151, 152 include surface mounted diodes 151 and surface mounted capacitors 152
making up the multiplier 12 as described with respect to FIG. 2.
In the illustrated embodiment, the primary windings 113 of the
transformers 11 are electrically connected in series and coated by an insulation body
114. The insulation body 114 is made of polypropylene (PP) or other insulation
material to insulate the primary windings 113 from the secondary windings 115. Each
core 111 is ring-shaped and each secondary winding 115 of the transformers 11 winds
around each core 111. The cores III encircle the insulation body 114 respectively.
The transformer module 5 is located on one side of the printed circuit board 4. The
pair of output terminals 116, 117 of the secondary winding 115 extend toward the
printed circuit board 4 and are electrically connected to the surface mounted diodes
151 and the surface mounted capacitors 152 on the printed circuit board 4.
The number N of the voltage-conversion modules 1 is optimally
determined according to a voltage of the X-ray tube 2 which is the targeted highvoltage
DC outputted from the power generation system 100, a current of the X-ray
tube 2, the switching frequency of the low-voltage AC from the power source 3, rise
and fall speed of the high-voltage DC, as well as voltage ratings of the diodes 151 and
the capacitors 152. As the number of voltage-conversion modules 1 increases, the
voltage rating of the diode and capacitor can be decreased. However, the complexity
and performance also needs to be considered in balance. The number N is an even
number between 4 and 24, so that the X-ray generation system 200 can use diodes and
capacitors with low voltage ratings, as well as has a low cost and a compact package.
Since the diode has a low voltage rating, the multiplier stage 15 can use only one
diode to achieve the desired performance and avoid diode damage resulting from an
unbalanced voltage.
The higher the switching frequency, the lower capacitance of the
capacitor 152 is required. Thereby, the X-ray generation system 200 may use
capacitors with lower capacitance. Surface mounted diodes and capacitors have low
voltage ratings. So the surface mounted diodes and capacitors can be utilized in the
X-ray generation system 200 for thin package. Additionally, the high switching
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frequency also benefits for high rise and fall speed of the high-voltage DC to reduce
X-ray radiation to patients.
While the invention has been described with reference to exemplary
embodiments, it will be understood by those skilled in the art that various changes
may be made and equivalents may be substituted for elements thereof without
departing from the scope of the disclosure. In addition, many modifications may be
made to adapt a particular situation or material to the teachings of the invention
without departing from the essential scope thereof.
Furthermore, the skilled artisan will recognize the interchangeability of
various features from different embodiments. The various features described, as well
as other known equivalents for each feature, can be mixed and matched by one of
ordinary skill in this art to construct additional systems and techniques in accordance
with principles of this disclosure.

WE CLAIM:
1. A power generation system, comprising:
an input to receive a low-voltage alternating current;
a number N of voltage-conversion modules, coupled to the input, and each
electrically connected in series and each comprising:
a transformer for converting the low-voltage alternating current into a
high-voltage alternating current; and
a multiplier for converting the high-voltage alternating current from
the transformer into a high-voltage direct current, the multiplier comprising a
positive multiplier part and a negative multiplier part, the positive multiplier
part and the negative multiplier part each comprising a pair of input terminals
connected in parallel with the transformer, and at least one multiplier stage
comprising a single diode and a capacitor assembly;
wherein the number N is an even number between 4 and 24.
2. The power generation system of claim 1, wherein the high-voltage
alternating current output from the transformer ranges from 300 V to 5000 V.
3. The power generation system of claim 1, wherein the high-voltage direct
current output from the multiplier ranges from 1.5 kV to 40 kV.
4. The power generation system of claim 1, wherein the diode is a surface
mounted diode with a voltage rating ranging from 600 V to 10 kV.
5. The power generation system of claim 1, wherein the capacitor assembly
comprises one or more serially connected capacitors and each capacitor is a surface
mounted capacitor with a voltage rating ranging from 600 V to 10 kV.
6. The power generation system of claim 1, wherein a switching frequency of
the low-voltage alternating current ranges from 100 kHz to 1 MHz.
7. The power generation system of claim 1, wherein a number of the at least
one multiplier stage in each of the positive multiplier part and the negative multiplier
part is between 2 and 8.
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8. An X-ray generation system comprising:
a power source for providing a low-voltage alternating current;
an X-ray tube having an anode and a cathode; and
a power generation system for converting the low-voltage alternating current
from the power source into a high-voltage direct current supplied to the X-ray tube,
the power generation system comprising a number N of voltage-conversion modules
electrically connected in series, the voltage-conversion modules each comprising:
a transformer coupled to the power source for converting the lowvoltage
alternating current into a high-voltage alternating current,; and
a multiplier for converting the high-voltage alternating current from
the transformer into the high-voltage direct current, the multiplier comprising
a positive multiplier part and a negative multiplier part, the positive multiplier
part and the negative multiplier part each comprising a pair of input terminals
connected in parallel with the transform and at least one multiplier stage
comprising a single diode and a capacitor assembly;
wherein the number N is an even number between 4 and 24.
9. The X-ray generation system of claim 8, wherein the high-voltage
alternating current output from the transformer ranges from 300 V to 5000 V.
10. The X-ray generation system of claim 8, wherein the high-voltage direct
current output from the multiplier ranges from 1.5 kV to 40 kV.
11. The X-ray generation system of claim 8, wherein the diode is a surface
mounted diode with a voltage rating ranging from 600 V to 10 kV.
12. The X-ray generation system of claim 8, wherein the capacitor assembly
comprises one or more serially connected capacitors and each capacitor is a surface
mounted capacitor with a voltage rating ranging from 600 V to 10 kV.
13. The X-ray generation system of claim 8, wherein a switching frequency of
the low-voltage alternating current from the power source ranges from 100 kHz to 1
MHz.
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14. The X-ray generation system of claim 8, wherein a number of the at least
one multiplier stage in each of the positive multiplier part and the negative multiplier
part is between 2 and 8.
15. A power generation package comprising:
a printed circuit board carrying a plurality of electronic elements comprising
surface mounted diodes and surface mounted capacitors; and
a number N of transformers each comprising a core, a primary winding and a
secondary winding, the secondary winding electrically coupled to the electronic
elements;
wherein the number N is an even number between 4 and 24.
16. The power generation package of claim 15, wherein each surface mounted
diode has a voltage rating ranging from 600 V to 10 kV.
17. The power generation package of claim 15, wherein each surface mounted
capacitor has a voltage rating ranging from 600 V to 10 kV.
18. The power generation package of claim 15, wherein the primary windings
of the transformers are electrically connected in series and coated by an insulation
body, each secondary winding of the transformers winds around one said core and the
cores of the transformers encircle the insulation body respectively.
19. The power generation package of claim 15, wherein the core is a ferrite
core or a nanocrystalline core.